Linzess (linaclotide) and Viberzi (eluxadoline) are both prescription medications used to treat different types of irritable bowel syndrome (IBS). Linzess is a guanylate cyclase-C (GC-C) agonist that helps with IBS with constipation (IBS-C) by increasing fluid in the intestines to ease bowel movements. On the other hand, Viberzi is an antidiarrheal that targets opioid receptors in the gut to treat IBS with diarrhea (IBS-D). Linzess is taken once daily on an empty stomach, while Viberzi is taken twice daily with food. Linzess can cause diarrhea as a common side effect, whereas Viberzi can lead to constipation and has a risk of pancreatitis, especially in people without a gallbladder or those who drink heavily. Additionally, both medications are only available as brand medications, while Viberzi is a controlled substance due to its potential for abuse.